In the long steep slope diversion tunnel with double tunnels and double bends,the spiral flow in the upper and lower bends could increase the flow range of mixed free-surface-pressure flow and the unsteady influence of the hy-draulic characteristics lead to increasing the difficulty of defining mixed free-surface-pressure flow and determining the diversion design flow.Based on the simulation of a three-dimension mathematical model,the process of changing the flow pattern in the tunnel from free surface flow to mixed free-surface-pressure flow,and then to pressure flow is de-scribed.It is proposed that the gas-carrying pressure flow is classified as pressure flow and is regarded as the boundary flow pattern between mixed free-surface-pressure flow and pressure flow.The hydraulic characteristics of mixed free-surface-pressure flow are defined.The relative acting head range of upstream is 1.61～2.40.The flow pattern is dis-continuous on the free surface and changes with time and space.At the same discharge,the reservoir water level fluc-tuates greatly,and the diversion ratio of the inner tunnel changes in a positive direction,while the diversion ratio of the outer tunnel changes in a reverse direction.The pressure characteristics along the way show alternating changes of pressure flow characteristics and open flow characteristics,and the action pressure turbulence is strong.
关键词
长陡坡导流隧洞/双洞双弯/明满交替流/压力特性/分流比
Key words
diversion tunnel with long steep slope/double tunnels and double bends/mixed free-surface-pres-sure flow/pressure characteristics/diversion ratio
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